PHEV heating modes to provide cabin comfort

Abstract

A vehicle is disclosed that has multiple coolant paths selected by control of a valve. A valve system is configured to direct coolant from an engine to a heat exchanger according to a difference between a temperature associated with the engine and a temperature associated with the heat exchanger. The valve system is also configured to direct coolant from the engine to an electric heater and to, in response to a heat demanded from the heat exchanger being greater than a heat capability of the electric heater, request the engine to run. A method is disclosed for controlling a valve to change from an isolation position in which the valve isolates coolant circulating through an electric heater and the valve from coolant circulating through an engine to a non-isolation position in which the valve directs coolant from the engine to the electric heater.

What is claimed is: 
     
       1. A vehicle comprising:
 an engine; 
 a coolant loop including an electric heater and a heater core; 
 a valve configured to selectively direct coolant from the engine to the coolant loop; and 
 a controller programmed to, in response to a heat demanded from the heater core being greater than a heat capability of the electric heater, operate the valve to direct coolant from the engine to the coolant loop and request the engine to run. 
 
     
     
       2. The vehicle of  claim 1  wherein the controller is further programmed to operate the valve to direct coolant from the engine to the coolant loop according to a difference between a temperature associated with the engine and a temperature associated with the heater core. 
     
     
       3. The vehicle of  claim 2  wherein the difference between the temperature associated with the engine and the temperature associated with the heater core is greater than a predetermined threshold. 
     
     
       4. The vehicle of  claim 1  wherein the controller is further programmed to operate the electric heater to heat coolant according to a difference between a temperature associated with the engine and a temperature associated with the heater core. 
     
     
       5. A vehicle heating system comprising:
 a controller programmed to operate a valve to change from an isolation position in which the valve isolates coolant circulating through an electric heater and a heater core from coolant circulating through an engine to a non-isolation position in which the valve directs coolant from the engine to the electric heater and request the engine to run in response to a difference between a heat demanded from the heater core and a heat capability of the electric heater being greater than a threshold. 
 
     
     
       6. The vehicle heating system of  claim 5  wherein the controller is further programmed to operate the valve to direct coolant from the engine to the heater core in response to the electric heater being inoperative. 
     
     
       7. The vehicle heating system of  claim 5  wherein the controller is further programmed to operate the valve to direct coolant from the engine to the heater core in response to a pump configured to circulate coolant through the heater core being inoperative. 
     
     
       8. The vehicle heating system of  claim 5  wherein the controller is further programmed to operate the valve to direct coolant from the engine to the heater core in response to a temperature sensor measuring the temperature associated with the heater core being inoperative. 
     
     
       9. The vehicle heating system of  claim 5  wherein the controller is further programmed to operate the electric heater to heat the coolant circulating therethrough according to the difference between the temperature associated with the engine and the temperature associated with the heater core.